The invention relates to a method for measuring the bearing play in a highly dynamic mechanical transmission chain with a setting member, which acts on a functional element and the interaction of which generates the bearing play to be measured.
In high frequency mechanical transmission chains, the setting members are moved in high frequency in particular to carry out an adjustment. Thus, the resulting bearing play of the transmission elements can increase very rapidly. When the resulting bearing play exceeds a specific size, the case occurs that a commanding transmission chain is moved with a phase delay in a specific direction of the setting member attached thereto. In so doing, the phase delay can amount to −180 degrees, whereby the control or damping effect that is intended by the setting member is not achieved, but rather an opposite effect. In particular, however, there is the danger that before such a phase delay can occur, the structural parts of the mechanical transmission chain have broken down due to the massive follow-up movements.
One example, to which the method of the invention can be applied, is the checking of the bearing play in controlled aircrafts, where the bearing play has to be observed and checked at regular intervals. In addition to the frequency of the required checking due to the continuous loads, the high frequency of the required bearing play measurements is also caused by the fact that such a measurement has to be taken for every change in the system lifting surface/control surface. However, the invention does not relate only to the checking of the bearing play in controlled aircrafts. The invention can be applied just as well to the checking of the bearing play in any type of flying devices as well as in general to highly dynamic mechanical transmission chains.
Another device or another method from the construction of aircrafts for measuring the bearing play of control surfaces is known from the DE 199 43 481 A1. In this case the actuator is moved into an arrested position by generating a predefined hydraulic pressure, by activating the electricity and by setting a predefined operating state of the automatic pilot. Furthermore, the control surface to be checked is loaded first in a first direction of movement by means of a weight; and in this load state the deflection is measured with a dial gauge. Then in a second step the control surface is loaded in the opposite direction. Then one can conclude the bearing play from the information of the dial gauge.
One drawback of this method is that to generate a weight in the opposite directions large gallows must be set up at least for one direction so that the complexity of the devices is not insignificant. Another drawback is that the process of ascending and removal of relatively large weights per measurement must be performed twice and repeated for all control surfaces. In so doing, first of all, the labor cost and secondly the storage cost of the weights and the measurement setups is very high. Since, furthermore, weights of up to 300 kg must be raised in partial weights of 20 kg, the carrying of the weights for the engineer taking the measurements is dangerous. In addition, the process is subject on the whole to risks, since it can never be totally ruled out that one of the control surfaces will not start to move as a consequence of the control movements of the dynamics and thus overthrow the measurement setup with the weights. Another drawback of the method according to the prior art is that each measured value of the dial gauge has to be read and entered manually on a log sheet, since for every work step the indicating dial gauge has to be recorded as a function of the weights to be raised manually. Irrespective of the onerous task of writing down, this method is subject to a high risk of errors. Similarly the manual input of the measured values into a computer constitutes a source of error that cannot be ignored.
Therefore, the object of the invention is to provide a device and a method for measuring the bearing play of a highly dynamic mechanical transmission chain, which is simple to set up, safe to use and guarantees a high degree of accuracy.
This problem is solved by providing a measuring device with a sensor for sensing the position of a functional element, whereby the sensor measures its distance from a reference point of the functional element, and a control unit which actuates the setting member by means of a square-shaped desired signal of half a period, wherein the bearing play is determined from the comparison of the actual deflection with the command signal of the setting member.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.